Thermometer



Dc. 1l, 1934.

E. BANDQLY THERMOMETER Filed Oct. l5, 1952 5 3m y 5 17M j@ J wwwINVENTOR Erich Bandoy BY www ATTORNEY Patented Dec. 11, 1934` UNITEDSTATES PATENT OFFICE THERMOMETER Application October I5, 1932, SerialNo.,637,975 7 claims.v (c1. vs -52) This invention relates tothermometers and more particularly to an industrial thermometer.

In thermometers having protecting stems, it has been customary to makethe stem Aand bulb chamber in two separate parts to enable suitablesealing material to be inserted into the lower end of the stem about thecapillary tube, so that conducting medium surrounding the thermometerbulb in the bulb chamber would be prevented from entering the stem. Ithas therefore been necessary to join the lower end of the protectingstem toA the bulb chamber by a separable connection, which hasresultedin an undesirable joint at the junction of these two parts.Furthermore, it is difficult to make a mechanically tight joint betweenthese parts so that frequently there is a leakage of the conductingmedium from the bulb chamber therethrough, and since the conductingmedium is usually mercury this leakage is particularly undesirable.

The main feature of the present invention resides in a protecting stemthermometer in which the stem and bulb chamber are integral and in whichthe conducting medium about the capillary bulb is confined to the bulbchamber.

A further feature of the invention resides in a protecting stemthermometer in which the seal between the spacein the protecting stemand the bulb chamber is adjustable at a point near the thermometer case.

For a clearer understanding of the invention, reference is made to thedrawing in which Fig. 1 is a front View of a thermometer including thepresent invention; Fig. 2 is a verticalsection of the lower part of thethermometer and a fragment of the lower part of the case somewhatenlarged over its showing in Fig. 1; Fig. 3 is a sectional view similarto that shown in Fig. 2 but with the case and its connecting piece andwith the protecting stem and its integral bulb chamber omitted; Fig. 4is a fragmentary sectional view illustrating a modied form of connectionbetween the case and the protecting stem;v and Figs. 5 and 6,respectively, represent in section a modified form of sealing means forthe bulb chamber before and after mounting in the protecting stem.

Referring especially to Fig. 1, 5 designates a thermometer case providedwith the usual scale plate 6 in front of which the upper portion of acapillary tube is supported in any well known manner. The capillary tube'7, as best shown in Fig, 2, extends through the lower end of the caseand terminates in a bulb 8 containing the usual expansive medium such asmercury. The lower ducting medium within the bulb chamber.

portion of the capillary tube '7 projecting through the case, extendsinto a metallic protecting stem 9 terminating in an integral bulbchamber 10 in which the bulb of the capillary tube 7 is positionedsubstantially as shown in Fig. 2. The upper end of the stem 9 has ascrew-threaded connection with a hollow connecting piece 16 surroundingtube 7 and supported by a screwthreaded connection in the lower end ofthe case 5. The bulb chamber 10 contains mercury indicated at 11, to llthe space between the inner wall of the chamber 10 and the bulb 8,thereby ensuring good heat conduction from the outside of the bulbchamber 10 to the bulb 8. This mercury is only necessary about the bulb8 and must be conned to the bulb chamber of the stem.

In former types of thermometers having a protecting stem, it has beenfound f necessary to make the bulb chamber 10 separable from the stem 9.the need for the proper mounting of the capillary tube with respect tothe other parts of the thermometer while sealing the mercury or othercon- By the present arrangement, it is possible to make the stem 9 andthe bulb chamber 10 in one piece, thereby eliminating the unsanitaryjoint which is present when these parts are made in Vtwo pieces. Thisarrangement also ensures the proper relationship between the capillarytube and its bulb with respect to the thermometer case, the stem and thebulb chamber.

For the purpose of conning the mercury 11 in the bulb chamber 10,suitable packing 12 is provided surrounding the lower portion of thecapillary tube 7 and engaging the inner wall of the stem 9 at a point onthe stem where it merges with the bulb chamber 10. The packing 12 may bemade of various materials well-known in this art but it is hereinillustrated, by way of example, as comprising a series of washers formedfrom asbestos impregnated with graphite or similar composition to makethe asbestos impervious to mercury. A sleeve 15 closely tting within thestem 9, is supported at its upper end on connecting piece 16 by ascrew-threaded connection and has its lower end engaging the top surfaceof the packing. A rigid washer 14 loosely tting `about the capillarytube 7, has an outer dimen- This necessity, in part, has arisen from dIt has been mentioned that the hollow connecting piece 16 is screwedinto the lower end of the case 6 and into the' upper ends of both thestem 9 and the sleeve 15. Thus, as the stem 9 is screwed into theconnecting piece 16 in the final assembly of the thermometer, the lowerend of the sleeve 15 forces the packing 12 into the tapered part of thestern 9 where it joins the bulb 10. In this manner, by compressing thewashers into the form shown in the lower part of Fig. 2, a mercury-tightseal is provided atthe open end of the bulb chamber 10 so that themercury cannot leak therefrom. By screwing the connecting piece 16 agreater or less amount into the sleeve 15, the compression of thepacking 12 may be adjusted to control the sealing of the bulb chamber.

In Fig. 4 there is shown a slightly different arrangement for joiningthe casing to the stem 9a, in which arrangement the upper end of thestem is screw-threaded into the lower portion of the case 5. However,the sleeve 15 is not screwthreaded at its upper end, but instead, thisend engages an internal shoulder of the case so that the lower end ofthe sleeve is forced downward to compress the packing or washers 12 inthe manner illustrated in Fig. 2.

In a further modified form of the invention, as illustrated in Figs. 5and 6, the packing washers 12 may be replaced by an annular packing 19formed of flexible material such as rubber and containing the coilspring 18 surrounding capillary tube 7. In this last-mentionedarrangement, when sleeve l5 is forced downward in the manner previouslymentioned, coil spring 1S is deformed as shown in Fig. 6, so that theflexible packing 19 closes the joint between the lower end of sleeve 15and stem 9a and also tightly engages the plug of cement 13, therebycausing a mercury-tight seal to confine the mercury in the bulb chamber.The spring 18 forces the packing 19 against the inner wall of stem 9aeven when this stem and sleeve 15 expand different amounts in responseto sudden changes in surrounding temperature conditions, so that a tightseal is insured under all conditions encountered during It will beunderstood that there may be numerous modifications and variations ofthe present arrangement within the scope of the following claims,without departing from the spirit of the present invention.

I claim:

1. In a thermometer, a case, an integral stem and a bulb chambersupported by said case, a capillary tube provided with a bulb having anexpansible medium therein, said tube being supported within said caseand said stem With said bulb positioned in said bulb chamber in spacedrelation to the walls thereof, a conducting medium in said bulb chambersurrounding said bulb, sealing material surrounding said tube andengaging .the inner surface of said combined stem and bulb chamber, asleeve surrounding the tube and extending from a point near said case tosaid sealing material for engaging the same, and a screw-threadedconnecting piece in screwthreaded engagement with the case, the sternand the sleeve to bring them in adjusted relation with respect to oneanother.

2. In a thermometer, a case, a hollow connecting piece fastened to saidcase, an integral hollow stem and bulb chamber fastened to saidconnecting piece, the junction between said stem and said bulb chamberhaving a tapered wall portion,

a capillary tube terminating in a bulb having an expansible mediumtherein. said capillary tube being mounted in said case and said stemwith said bulb positioned in said bulb chamber in spaced relation to theinner surface thereof, a conducting medium in said bulb chambersurrounding said bulb, sealing means engaging said Jtube and the taperedwall portion, a hollow sleeve surrounding said capillary tube and havingits upper end adjustably fastened to said connecting piece and havingits lower end engaging said sealing means to compress the same againstthe tapered wall portion.

3. In a thermometer, a case, a hollow connectling piece fastened to saidcase, an integral hollow stem and bulb chamber fastened to saidconnecting piece by a screw-threaded connection, the junction betweensaid stern and said bulb chamber having a tapered wall portion, acapillary tube terminating in a bulb having an expansible mediumtherein, said capillary tube being mounted -in said case and said stemwith said bulb positioned in said bulb chamber in spaced relation to theinner surface thereof, a conducting medium in said bulb chambersurrounding said bulb, sealing means engaging said tube and the taperedwall portion, a hollow sleeve surrounding said capillary tube and havingits upperend fastened to said connecting piece by a screw-threadedconnection and having its lower1 end engaging said sealing means tocompress the same against the tapered wall portion.

4. In a thermometer, a case, a hollow integral stem and bulb chamber,said stem being connected to said bulb chamber by a tapered portion, acapillary tube terminating in a bulb containing an expansible medium,said tube extending from a point in said case through said stem and withits bulb positioned in said bulb chamber in spaced relation to the wallsthereof, a heat-conducting medium in said bulb chamber, sealing meansengaging said tube and the reduced portion of said stem and said bulbchamber, a hollow sleeve having its upper end engaging a part carried bysaid case and its lower end engaging ,said sealing material to compressthe same against said tapered wall portion.

5."In a thermometer, a case, a capillary tube terminating in a bulbcontaining an expansive medium, said tube having a portion extendinginto said case, an integral stein and bulb chamber supported on saidcase and enclosing the remainder of said tube and its bulb with saidbulb extending into said bulb chamber, the junction between said stemandsaid bulb chamber including a tapered wall portion, a heat conductingmedium in said bulb chamber, sealing means surrounding said tube andengaging the inner wall of said stem, said sealing means includingpacking material and a spring, and means within said stem for forcingsaid packing material into engagement with the tapered wallportionagainst lthe action of said spring. k

6. In a thermometer, a case, a hollow integral stem and a bulb chamber,said stern being connected to said'bulb chamber by a portion of reduceddiameter, a capillary tube terminating in a bulb containing anAexpansible medium,` said tube extending from a point in said casethrough said stem and with its bulb positioned in said Vbulb chamber inspaced relation to the inner surpacking and a coil spring substantiallyenclosed by said packing, and a sleeve Within the stem engaging saidpacking to compress the stem against the action of said spring.

7. In a thermometer, a case, a capillary tube terminating in a bulbcontaining an expansive medium, said tube having a portion extendinginto said case, an integral stem and bulb chamber supported on said caseand enclosing the 10 remainder of said tube and its bulb With said bulbextending into said bulb chamber, the junction between said stem andsaid bulb chamber having a tapered Wall portion, a heat-conductingmedium in said bulb chamber, sealing means surrounding said tube andengaging the inner Wall of said stem, and means Within said stem foradjustably forcing said sealing material against said tapered Wallportion.

